Field of the Invention
The present invention relates to a method of producing a toner that is used in recording methods that utilize an electrophotographic procedure, an electrostatic recording procedure, or a toner jet recording procedure. The present invention also relates to a method of producing a resin particle.
Description of the Related Art
Resin particles are used in a broad range of fields as highly functional powders, and, in order to control their functionality, monodisperse resin particles having a narrow particle size distribution are frequently required. In the field of electrophotographic apparatuses in particular, there is unending demand for enhancing image quality, and uniform properties among the particles are thus required of the toner particles that form the image. It is effective in pursuing this to inhibit the generation of low-circularity irregular-shape particles together with providing a uniform toner particle diameter and a sharp particle size distribution.
The “dissolution suspension method” is known to be a production method that can readily achieve a sharpening of the particle size distribution and a higher circularity for toner particles. The dissolution suspension method is a method in which a resin solution is preliminarily prepared by dissolving a resin in an organic solvent, this resin solution is dispersed in a dispersion medium and a dispersion of droplets is formed by the resin solution, and particles are subsequently obtained by removing the organic solvent from the dispersion. An aqueous medium is generally used as the dispersion medium in the dissolution suspension method, but this approach requires very large amounts of energy and time for a washing step and drying step after the particles have been formed.
In Japanese Patent Application Laid-open No. 2009-052005, a method for producing resin particles by the dissolution suspension method is described that uses liquid-state or supercritical-state carbon dioxide as the dispersion medium. In this method, particles are obtained by introducing liquid or supercritical carbon dioxide after the formation of the dispersion of droplets with the resin solution and by carrying out solvent removal by extracting the organic solvent. With this method, the particles can be easily separated from the dispersion medium by depressurization following particle production and a low-energy production is made possible because a washing step and drying step are not required.
Japanese Patent Application Laid-open No. 2010-132851 describes a method in which resin particles having a core-shell structure are produced by a dissolution suspension method using carbon dioxide for the dispersion medium; here, resin fine particles resistant to swelling by carbon dioxide are used as a dispersant with the goal of preventing the droplets from aggregating and the shell is also formed by these resin fine particles.
In Japanese Patent Application Laid-open No. 2011-116976, a production method is described in which, in a dissolution suspension method using carbon dioxide for the dispersion medium, the solvent removal efficiency during solvent removal is raised by bring about the crystallization and solidification of a resin dissolved in the droplets.
In Japanese Patent Application Laid-open No. 2013-137535, a toner particle is described that uses a resin fine particle that contains a comb-structure resin for which the essential constituent components are a segment having an organopolysiloxane structure and a segment having an aliphatic polyester structure.